Leptin, ghrelin, endocannabinoids Flashcards
What is leptin?
A peptide hormone secreted by adipose tissue
blood leptin levels are proportional to:
adipose tissue mass
Where does leptin act?
primarily on the arcuate nucleus of the hypothalamus on both NPY and POMC neurons
What does leptin do to NPY and POMC neurons?
- inhibits NPY neurons
- stimulates POMC neurons
2 aspects of hypothalamic neuronal circuitry affected by leptin:
1) direct neural signaling via NPY and POMC
2) altering wiring patterns by creating more stimulatory POMC synapses and less stimulatory NPY synapses
Ultimate result of leptin activity:
- decreased appetite
- increased energy expenditure
- keeps amount of adipose tissue within certain range
genetic mutations that can lead to obesity
1) leptin gene
2) leptin receptor gene
3) a-MSH gene (a-MSH released by POMC neurons)
4) MC4R gene (receptor for a-MSH)
limitations to leptin injections
1) only help when person either does not produce leptin or produces defective leptin
2) very low percentage of obese people have low leptin levels, most have higher than normal leptin levels
possible connection between leptin and failure in dieting?
Dieting causes decrease in adipose tissue and therefore decrease in leptin levels. Decrease in leptin signaling causes increased NPY and decreased POMC neuron activity. Also, person still has longer term wiring patterns of a heavier person. Result is a fight against biological drive to eat more and expend less energy.
If leptin regulates then how to people become obese in the first place?
other factors: sight, smell, volition
what is ghrelin?
peptide hormone secreted by the stomach
ghrelin secretion is inversely proportional to:
stomach distention (empty stomach means lots of ghrelin)
where does ghrelin act?
on the arcuate nucleus of the hypothalamus on NPY neurons
How does ghrelin act?
activates NPY neurons (opposite to leptin)
what are endocannabinoids?
derived from low-abundance phospholipids, they are released from the cell surface in response to stimulation
